The efforts of this research group is to demonstrate the participation of the T-cells in immunopathology of syphilis. Various approaches are considered. The T and B lymphocytes from experimentally infected rabbits are separated and examined in the presence of treponemal and non-treponemal antigens for the production of factors inhibiting stimulating leukocytes migration. Similar experiments are conducted using cells from patients with various stages of syphilis. Leukocytes of rabbits infected for some time with T. pallidum may react with homologous organ extracts. It is feasible that cells of patients will cardiovascular syphilis, neurosyphilis or gummatous lesions on other systems may also react with extracts of human organs. Experiments in this line are conducted.